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Is the phraseology in the early portion of the movie The Net realistic?
Bear with me for a moment; I know that this is based on a movie scene, but there's a real question at the end.
Early in the 1995 movie The Net, there's a scene where a programmer is flying their Cessna at or near dawn, approaching the destination airport. This is a night flight, so it would presumably be an IFR flight with all of what that means, or rather meant in the mid-90s. We get to hear some communication between the pilot and ATC:

(pilot) Burbank tower, Cessna seven-three-nine-Mike-Bravo, intercepting approach course, ILS runway eight.
(ATC) 39 Mike Bravo, we've lost radar contact. Say your position and altitude.
(pilot) Just passing the middle marker at 1300 feet.
(ATC) 39 Mike Bravo, that's a negative. Verify your position and check your instruments.
(pilot) All normal, for crying out loud, you must be able to see my lights.
(ATC) That's a negative. Execute a missed approach immediately. Contact approach control on one-two-four point five.

A moment later,

 the airplane crashes into what appears like it could be power station chimneys, and turns into a fireball, killing the pilot.

That ATC exchange has always bothered me. I can see a few things that feel obviously wrong:

It seems awfully late, especially in IFR towards a big airport (assuming that's Hollywood-Burbank, which goes nicely with a later in-movie statement that this happened "outside L.A."), to contact ATC only by the time you are well into the final approach.
If this is an IFR flight, shouldn't the pilot be following a filed flightplan, and wouldn't someone notice if the aircraft strays too far from its intended course and at least ask the pilot what's going on then rather than wait until it is well into populated or industrial areas? (Note: I can't tell from the movie if the plane supposedly has a transponder or not.)
By the time of passing the middle marker, shouldn't the pilot have the runway clearly in sight and at the very least be lining up with it, if not already be fully lined up with it? This is in moderate darkness, but it doesn't appear to be in otherwise difficult conditions; no visible fog, for instance, even in aircraft-exterior shots.

If someone wants to comment on the above as well, feel free to. However, my main question is this: if this situation were to somehow develop in real life, then is the phraseology realistic? Would ATC say that they have "lost" radar contact? Since the aircraft is obviously in the wrong place by that time, it would seem like they should never have had radar contact in the first place. In such a situation, I (as a non-pilot) would expect ATC to request an ident, possibly verifying the transponder code as well.

I hope I tagged this correctly.

"that's a negative. Verify your position and check your instruments" - yet they lost radar contact, so how do they know it's incorrect?

@SteveKuo Extra-sensory perception? Or knowing which direction to look in and not seeing any aircraft navigation lights? (That latter is how I've explained that particular comment to myself...) After all, the pilot is giving a supposed heading to the aircraft (the inverse of ~80° along the runway) and supposed distance ("middle marker"), so someone who knows where those are should know where to look given that. If there's nothing there, then, well...

"Radar contact lost" is standard phraseology.  Most typically it's used when an aircraft far from the radar antenna is no longer being picked up, and it's just an advisory that "we can talk to you but we can't still see you."  (Remote VHF antennas are cheaper & easier to put up in remote places than radar transmitters.)
As for the scenario itself, initial contact with the tower is hardly the point where ATC would first notice that the aircraft wasn't going where it should be.  To get TO the ILS course, you'd typically have Approach Control issuing radar vectors to the aircraft, ending up with "N1234X, 3 miles from Van Nuys, fly heading 100 until established, cleared ILS runway 8 at Burbank."  If the aircraft flies through the course (for whatever reason; it sounds like in the movie the implication is that his navigation equipment has been hacked), they'd issue another vector, cancel his approach clearance & tell him to climb, or whatever.
Also, ATC (i.e. Approach Control, even more so than Tower) will get automated low altitude alerts when an aircraft is below set altitudes.  If an aircraft in radar contact was descending into terrain (and not on final to a runway), well before the radar loses line-of-sight with the aircraft, the controller would issue something along the lines of "N1234X, low altitude alert, check altimeter 30.05, climb and maintain 2000'."
There are non-radar environments where pilot mistakes have put perfectly flyable aircraft into the terrain without any opportunity for ATC intervention.  There have been cases within radar coverage where misread instruments, usually only when combined with an additional pilot error, have put aircraft into terrain or obstacles short of the landing runway.  The smokestacks referenced sounds like a prominent feature well north of Burbank, so at a minimum there's some "artistic license" involved in claiming that a hacked ILS could put the aircraft that far off course in that direction without ATC catching it well in advance of things getting to the point of a crash.
Also, an ILS receiver would be awfully hard to hack, no matter what sort of evil programming genius you are.  You could disable it in several different ways (pair of wire cutters would do that), but the malfunction would be obvious to the pilot early on.  To have the receiver seem perfectly normal but in fact guiding the pilot down too soon would really require broadcasting false signals to the aircraft in real time in a way that an ILS ground station probably can't do -- at least not without triggering a warning in the monitoring equipment that ends up shutting it down.  And even then, when the pilot gets to 200' above the runway elevation, if HE doesn't see the runway lights, he should be going around.
All in all, this scenario has its weaknesses.  The idea that a hacker could create enough problems to bring down a plane is actually more credible now than in 1995, but even so, the most likely problems are a lot less dramatic than what's described -- "hey, where'd all my electronic charts go?"  Aviation has a LOT of safeguards to prevent exactly this sort of scenario from playing out, even with state-sponsored bad guys as the potential threat.
But, it made for a fun movie, so suspension of disbelief and all, right?

My favorite movie ILS hack was in Die Hard 2, where the terrorists, with a few clicks on the keyboard, made the glide slope antenna sink 50 feet into the ground!

@TomMcW With no degredation of signal quality for approaching aircraft, I'm sure?

@MichaelKjörling I believe you could mess with the glide slope and get it to fly you too low, but it's not something you could do remotely. You'd have to have physical access to the equipment. Since it works on amplitude one could boost the 90Hz signal and the instrument would continually think you were too high. Getting the pilot not to notice the discrepancy would be the next trick

Then again, the guys on KAL 801 killed 228 people when they followed an errant glide slope signal right into the ground

@TomMcW  Actually on KAL 801 in Guam, the GS was out of service, and they descended all the way down to Localizer mins right after passing the marker, instead of stopping at the step-down fix that would have kept them clear of Nimitz Hill.  That was one of the cases I had in mind with the "an additional pilot error" comment.  They knew they were descending dive-and-drive to LOC mins, but they missed the stepdown on the chart.

@RalphJ I'll have to read up on that one. The Mayday episode on it explained that the GS was notam'd as inop, but the GS needle on the captain's HSI started moving, for whatever reason, so they used it. I see the wiki article is citing outdated approach plates and confusion about the DME location.

@TomMcW https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0001.pdf#page153 The captain briefed the Localizer approach, but not the stepdown altitude. Not seeing any mention of following GS indication (tho wikipedia mentions it -- I'll take the NTSB as authoritative). The DME confusion is mentioned by the NTSB, tho not as causal, since the numbers on the charts were correct.

@TomMcW Messing with the ILS transmitter (including antennas and related infrastructure, whether remotely or locally) would have another disadvantage in this particular case: it would (should?) affect all aircraft equally. That would crash aircraft indiscriminately until someone catches on and announces the ILS as defective (which I suspect under IFR conditions would shut down at least the runway). The antagonists in the movie are portrayed as very much targetting specific people -- in most of the cases that we see, people who are out to help the protagonist or might be in a position to do so.

There is one very close call caused by a faulty GS. An ANZ 767 got down to 400ft AGL before they noticed a problem and went around. They apparently were prompted by seeing city lights. Had there been a thick fog it's possible they could have flown right into the ground


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Do airlines record the plane roll, yaw, pitch angles during a landing? (eg every 100 milliseconds)
We had a very wobbly landing in Washington DC today with United airlines. I was curious what the maximum roll angle (left right angle with ground) was during it.
Other information that I'd find interesting to know:

statistics on what that maximum angle was historically for flights that landed safely
the pilot and co-pilot's names

Related to : How dangerous was the turbulence on this commercial flight?
Update: added angle name and pilot name as interesting data

Are you talking about the yaw angle with respect to the runway? Because I don't know of any airplanes that are even capable of recording that information (aside from maybe some research airplanes with extra instruments installed).

Maybe the black box records it but that data would not readily be accessible.

@HiddenWindshield I meant the roll angle. For my purposes, any of roll, yaw, or pitch angles are interesting

@Bageletas thanks. What about the pilot's name?

why would they divulge the pilot's name?

Just ask for the full Karen.

@Federico why not?

because there is no need to hang out dry an employee like that if nothing happened. Either an accident or accident happened and there is an investigation, and the investigator can access that data, or releasing such info is just detrimental to the employee that ends up being harassed for just doing their job.

@Federico thanks. I understand the security implications now. I also just found this page that highlights that the names are announced at the beginning of each flight https://www.quora.com/How-can-l-find-the-pilots-name-with-the-flight-number-and-date?share=1

maybe the first names, not the full ones

Few passengers are qualified to asses whether the landing was wobbly or the whether the roll angle was unusual or dangerous.

@DaveGremlin one could argue the same for food/medicine ingredients, but it's still listed on the product

@Shadi  True, but with food or medicine, anyone could look up contraindications etc. do some research and inform themselves about safety.  Flying isn't like that, you can't train up as an airline pilot then do some crosswind landings to find out what is unusual or dangerous.  Even frequent flyers won't be familiar with things that are perfectly normal but don't occur often.  I've heard people describe what they thought were nightmare experiences but were actually completely safe - missed approaches, crosswind landings, light turbulence seem alarming if you don't understand what's happening.

@DaveGremlin Agreed. One of my listed points above is statistics about the distribution of these angles over a history of flights. Something along the lines of "the maximum roll angle of your flight was 5 degrees and it was reached in 1% of flights from 2000 till today with no crashes". Is such a statistic too far fetched? I'm no aviation expert, and I'd completely understand that there are many more entangled parameters, making it unfair to look at one parameter at a time. I'm also sure that it takes a lot of skill and experience to make any judgements. I'm not trying to replace that.

Btw thanks for engaging in this discussion with me. It's very educational.

@Shadi  I'm happy to discuss this, I'm only a hobby pilot so I can't give definitive answers.  The problem with the stat "the maximum roll angle of your flight was 5 degrees and it was reached in 1% of flights from 2000 till today with no crashes" is the still no crashes bit, as if bank angle is an indicator of a crash.  Bank angles will be well above this when turning, and on approach the pilot may bank to stay aligned with the runway https://aviation.stackexchange.com/questions/22678/on-crosswind-landings-is-it-preferable-to-side-slip-or-crab-on-final-approach#22686

@Shadi  Also, what would constitute a 'crash'?  A wingtip strike such as this https://www.avherald.com/h?article=49b23c6e&opt=0 where no-one was hurt?  Typically, AVHerald.com categorises events into Incidents, Accidents and Crashes.  I've had a quick look there and can only find one Crash; a small cargo plane: https://www.avherald.com/h?article=4a88f341&opt=0  There seem to be lots of Incidents and Accidents that have resulted in a wingtip or engine pod strike but no injuries to the crew or passengers.  That crash is very odd since the SD 330 is a high wing plane and was banked at 42º.

Yes, the type of data you are asking about does exist, but it isn't available for curious passengers to critique.
Most modern airlines have within their safety programs a means to record and analyze data and flag events that exceed certain parameters and are on the margins of safe, or "normal" operations.  The event can then be reviewed in greater detail by experienced flight crews and safety experts with the intent of determining whether or not any procedures were violated.  This is all done in the interest of improving safety, not for explaining to someone why a certain landing felt "wobbly".
There is some additional information in the article here:  Flight Safety
Something would have to rise to the level of a reportable accident for the NTSB to get involved, and for the results of the investigation to be made available to the public.

Why is it not publicly available? Is it just because it has always been this way?

Presumably for the same reasons your company doesn’t make HR records public.  What good would it do?

TBH I'm not convinced. @DaveGremlin above made a similar comment, and my reply was that the same logic could apply to food/medicine ingredients. But these are still made public.

@Shadi, ingredients are made public because it is a labeling requirement.  Companies otherwise have no incentive to list them.   What line of work are you in?  Maybe I can provide a better comparison that’s closer to your reality…

True. I was only arguing against your initial point of "what good would it do". The incentive being absent from companies is convincing. I personally hope that some day someone brings in regulations to make this data public. We have the technology for it, and it's not something that gives away any competitive advantage. It just gives a clear metric for quality control, and more eyes on it will help catch problems if any (instead of giving companies a hiding spot by shoving stuff under the carpet). It could even be used for marketing. I'm a data scientist, but no need for an example. I get it

Btw thanks for engaging in this discussion with me. It's very educational.

Honestly, @Shadi, if you had full access to the information, what would you do with it? Would you complain that the roll angle on your landing was 1° greater than the average landing and attempt to sue the carrier/pilot because you felt a bit nauseous? Would you complain if it was 1/2° beyond the design spec for 0.5 seconds, even though the plan made it safely to the ground, that info had already been reviewed by the airline (and probably the mfgr), the aircraft had already been inspected & deemed to still be airworthy?

As a bit of a data geek, I agree that it might be interesting to have this info, but it opens the airlines, aircraft mfgrs, and CAAs to far too many lawsuit possibilities (especially in the USA) from uneducated passengers who expect everything to be as comfy as sitting on the couch in the living room with the TV dulling their senses and get "scared" by a "wobbly" landing that was nothing more than a light gust of wind, well within parameters...

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Did the Nazis ever have a pulse jet hovercraft?
I recently read an article about experimental aircraft Nazis had made during WW2. And one aircraft caught my attention.It was a experimental aircraft Named “Die Glocke” It was first described by a polish journalist who claimed to have seen the aircraft. Does anyone know of any real proof that such aircraft existed? Also, would it have been possible to build it?

If it had gotten to the prototype stage, there would certainly be pictures somewhere.  I was always more impressed by the fact that they had a heavy lift helicopter in operational use.

What article were you reading?

There is no indication that Nazi Germany made any significant efforts towards hovercraft development, jet-powered or otherwise. Also, "Die Glocke" specifically is generally thought to be a relatively-recent conspiracy theory/hoax.
Polish author Igor Witkovsky specialises in... "historical" books exploring Nazi wonder weapons. The english wiki article on "Die Glocke" identifies him as the point of origin for this rumour; there seems to be no mention in any media of this contraption prior to publication of his book "Prawda o Wunderwaffe" in 2001 (note that Witkowsky also published a book dealing with Nazi UFOs in 1997, and it had no mention of "Die Glocke"). The author claims that Germans managed to create a device capable of controlling gravity, and that's what this machine was. I am not going to discuss here why this specific claim is ridiculous, if you are interested, you may ask on Physics.SE about it. Obviously, such aircraft never existed.
Since you are not asking about a gravity-defying flying saucer, but a much more reasonable hovercraft - let's also discuss if this or similar aircraft could actually be built during WW2. There is no known hovercraft developed in Nazi Germany, save for the failed Austrian project for a hovering torpedo boat undertaken in early 1930s. Moreover, the only more-or-less successful project of a jet-powered flying saucer (the Avro Avrocar) demonstrated several significant problems which any similar project would encounter; these issues are unlikely to be able to be resolved in the environment late-war Germany was - strapped for resources and with jet tech much less mature than it was in 1959. Some work were done on more conventional circular-wing aircraft (aircraft of Arthur Sack), but again, compared with a more mature design by Vought, it is unlikely that issues encountered in Sack AS-6 would be resolved before the end of the war. Thus, it is extremey unlikely any craft that would be remotely similar to the description of “Die Glocke” could make it off the ground in Nazi Germany.

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Why do we say "climb" and not "ascend"?
The term for moving to a lower altitude is "descending." Why, then, is the term for moving to a higher altitude "climbing" and not "ascending"? The latter goes better with the term "descending."
Does it have anything to do with "ascend" and "descend" sounding similar on the radio?

Perhaps a question for the English Language & Usage site, as it is certainly not limited to aviation.  We generally speak of climbing mountains & ladders, and of descending them.

@jamesqf Interesting. I don't think that I've ever heard anybody talk about getting down from a mountain or ladder. I may follow your suggestion.

While climb is probably a more common word for "going up something" than ascend, I don't think there really is a single-word antonym for it, other than descend.

One of the most important goals of standard phraseology in radio communications is to ensure that words are distinct enough that a momentary garble doesn't ruin understanding of the transmission. (This is also why a phonetic alphabet is used -- Alpha, Sierra, Foxtrot, etc., rather than just saying the letters A, S, F, ... Imagine if ATC told you on voice something like "taxi to runway 7 via S, hold short F4" and now instead make it "taxi to runway 7 via Sierra, hold short Foxtrot four". Which is less likely to be misinterpreted?)
Another goal, of course, is to have a limited vocabulary of distinct terms that can be used to state things between people who may not be all that familiar with the language.
As you correctly note, "ascend" and "descend" sound very similar. If you for whatever reason miss out on the first syllable, they're outright identical! I'd call it a Bad Thing (tm) to have a single syllable potentially making the difference between just another day at the office, and a mid-air collision.
So when faced with the choice of whether to say "climb" or "ascend", in light of the fact that we're already using the term "descend", it makes sense to use a clearly distinct term for the opposite case to clearly differentiate the two. Hence "climb". The same argument can be applied to the case of both terms being selected together, without either having been selected before the other.
As an aside, "maintain" is also clearly distinct from both, further reducing the risk of confusion. If your altimeter reads 5,000 ft and are asked to "climb to 4,000 feet" or "maintain 6,500 feet" (as opposed to climb and maintain), then you know that someone needs a reality check, and can ask for clarification, even if that request for clarification is only along the lines of "say again assigned altitude and QNH".

you are absolutely correct it is because they sound simila same goes for affirm and negative or flight level one hundred and flight level one one zero etc....

See Also: Using Affirm instead of Affirmative

@Dan Yes. The same basic reasoning would seem to apply.

You said that we are already using the term "descend." Is there a particular reason that we chose it and not some other word?

@wecsam I said that if you've already chosen to use "descend", it makes sense to not use "ascend". I also said that the same argument can be made if the two are chosen at the same time. Some word is needed, and at one point or another, which synonym to use becomes an arbitrary choice of one over the other. There may be some specific reason why "descend" was chosen to represent a reduction in altitude, but I'm not aware of it; that might be a decent separate question, though.

@wecsam: Perhaps we use descend for going down simply because there is no other common English word with that meaning.  So it's not as though we have a choice :-)

@jamesqf If ATC had originated in the UK, there's always the possibility that standard phraseology would have turned out to become "may we be so rude as to implore you to reduce the distance between mean sea level and your choice of point on your aeroplane, at your earliest convenience, to a distance somewhere in the vicinity of 33,000 feet as reported by onboard equipment, to the precision required to comply with all applicable regulations?". I think I prefer "descend flight level 330" for brevity.

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For how long is an engine start clearance valid?
If a pilot receives a clearance to start the engines, is the clearance void if he doesn't start them within a certain amount of time? How much time is allowed for starting the engines and where is it documented?
I'm asking for Thailand, but would like to know what the ICAO SARPs say.

In which country are you asking about?

Thailand, please. But how about the standard annex_? Thanks.

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Why does the trailing edge have a more pronounced taper than the leading edge on the Cessna 172?

Why does the Cessna 172 have a more pronounced taper on the trailing edge as opposed to the leading edge?

That's just the natural taper you get when the spar is straight in plan view, and the spar depth and airfoil is shrinking as it gets to the tip..
The chord is constant out to the strut attachment so the LE and TE is parallel. As the airfoil gets thinner outboard of that, if you keep the same profile it shortens chordwise as it gets thinner. Since the taper's neutral axis, the spar, is near the front at 15 or 20% of chord, the apparent taper in plan view seems more extreme at the TE.

Maybe you can add this cutaway to your answer to help visualise your point

@sophit Great idea thanks.

It could be argued that there is nothing "natural" about this. It is an engineering decision on how to balance conflicting goals, including performance in various flight regimes and cost of manufacture as examples of two conflicting goals (designing for better performance would cost more to produce).

"Natural" simply means the normal geometric result of tapering thickness with the same airfoil profile and a neutral axis forward. You are reading way too much into it.

You know, I never thought of it as a "natural" taper, but something the Wright Brothers found out in their early (low subsonic) wind tunnel experiments was that taking a little off the trailing edge corners of the "Hershey Bar" wing does save a little in drag.
Some like a rounded trailing edge, but a simple taper is easier to manufacture.

The balance between "empirism, performance, cost of manufacturing" behind the fact that all medium passenger jets are boringly equal.
If you excel in the first and third parameters, your name is Boeing or Airbus.
In the second and third, your name is Lockheed Martin or Mikoyan-Gurevich
If you excel in the first and second: Hi Burt Rutan, how are you?


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What is a rule of thumb for when to begin a descent?
What rule of thumb would you use for your airplane insofar as how far from your destination you would begin your descent given an expected straight-in approach and landing in no-wind conditions and no ATC or traffic restrictions? How would your weight influence that rule of thumb, bearing in mind that the heavier you are, the more potential energy you have to dissipate?
With those same conditions, what rule of thumb would you use to determine how close to the airport you could get before descending and still come straight in if you had an empty airplane save for necessary fuel and if you were allowed to use any aircraft configuration you wanted, and what would that configuration be?

If on an IFR approach, my understanding is the approach plates tell you these details (caveat: I'm not IFR rated). Flying VFR, my opinion is there's no reason that trumps safety to fly a straight-in approach and that an insistence on it just demonstrates a hazardous pilot attitude. It's much safer to slow things down in the pattern, giving you time to see the airport and other traffic (some of which might be NORDO) and time to properly plan your landing, even at airports you've never seen before.

@mah It's fairly common when flying IFR, especially to smaller airports, for ATC to clear you direct to the airport and to give you a descent "at pilots discretion" . I'm this case, you will be landing straight in and planning your own descent.

Terry, asking this "for your airplane" makes this question very broad, and there is no "one right answer". I would suggest changing it to "for a typical heavy jet" or whatever you would be most interested in.

@mah: The plates define the altitudes for the the approach (from IAF onward) and sometimes for final parts of the arrival (before IAF), but never from the en-route flight level.

Descent planning for jets can get a little tricky at times, and you have pointed out some of the things to look at when deciding when to start down (assuming that ATC gives you the option to choose your own top of descent).
The descent point is dependant on your aircraft and how much drag there is at your descent speed.  Anything that adds more drag allows you to come down faster, but also makes the flight less efficient since you would have burned less fuel had you just started down earlier without the drag.
A typical jet will descend with the engines at flight idle and the speed at the recommended descent speed, which is usually close to the maximum speed for the airplane.  A good rule of thumb for most jets would be:

3 miles for each 1,000 ft. of altitude to lose + 1 mile for every 10 KIAS of airspeed that you need to lose before landing.

Example:
We are cruising along at 38 thousand feet and landing at an airport with an elevation of 2 thousand feet which means that we need to lose 36,000 ft.  Let's say that we will be descending at 350 KIAS and need to slow to 150 KIAS for landing:

Thousands of feet to lose: $38-2=36$ thousand feet
  Tens of KIAS of airspeed to lose: $35-15=20$ tens of KIAS
Distance = $36\times3+20=128NM$ from your destination

So in this case, we will start down 128 miles out.
There are various factors that can cause this to be a little off, the biggest being the wind.  As the descent progresses, you should mentally double check your progress.  In this case, maybe check when we have 20,000 ft to go (should be 80 NM out now) and when we have 10,000 ft to go (should be 50 NM out now).
If one of your checks indicates that you are a little off, you can adjust your descent rate (adding a little power or using spoilers to descend more quickly) to get back on track.
A slight variation of this uses the same calculations, but instead of using the airport as the "target" altitude and speed, they use a point 30 miles from the airport at 10,000 ft above the airport at 250 KIAS.

The above method is enough to get someone started, and just "works" most of the time.  As a pilot becomes more comfortable with the math, they can start to make adjustments for other factors like:

The effect of the winds at the various altitudes during the descent

Headwinds mean that you can wait a little longer to descend
Tailwinds mean that you should start down a little sooner

Weight of the aircraft

The lighter the aircraft, the later you can start your descent.  (If this seems backwards, consider that when you are heavy it will push the airspeed higher faster as you lower the nose and you will have to raise it to keep from overspeeding.  When light, you can keep the nose further down and will therefore have a higher descent rate.)

The direction that you are approaching the airport from

If you are landing straight in you should start sooner
If you are going to fly a downwind, base, and final, you can start a little later

ATC speed restrictions can prevent you from descending at your normal rate, so you may need to start down earlier.
Inoperative equipment (i.e. spoilers, etc.) may keep you from descending as fast so you may need to start down earlier.

As far as the configuration of the aircraft, in order to get the most fuel efficient profile, I would keep it clean as long as possible and start the descent at a point where I could glide for the majority of the descent and configure on speed for a stabilized landing in the normal landing configuration for the aircraft.  If this is your goal, then the use of spoilers is an indication of poor planning!  ;-)

Since you try to tackle most of the things that could throw off your calculation, you could mention that unpressurized aircraft have a much more limited rate of descent.  Even though most jets are pressurized, some readers may be thinking of GA aircraft and even planes capable of pressurization may have pressurization inoperative due to maintenance issues.

For ATC planning of jet transport aircraft, 3NM per 1000 ft, plus 10 NM for deceleration is used as a rule of thumb.
$$FL300=3\times30+10=100NM$$
Most of the 10NM for deceleration will be consumed at around FL100.
Weight should not change the descent distance a lot, it mainly affects the speed. The lighter the slower.

In addition to this rule of thumb, absent a crossing restriction into smaller fields, I would plan cross 10k feet approximately 30nm from the field if relatively straight in, closer if we were expecting a downwind leg.

Well, you did say 'for your airplane'...
In a DA-42, with a cruise speed of 150kts, the game is to arrive at the FAF, at the intermediate approach altitude, at about 120kts. Or even better: be at that altitude and speed about 1NM before FAF so you still have 15 seconds to spare.
So:

5NM for each FL/1000' to descend (500fpm at 2.5NM a minute)
+1 NM for each 10kts to slow down (usually it's 30kts so 3 NM). If I'm heavy(er) I'll use 1.5NM for each 10kts
+1 NM for each 10mb above 1013, or minus for lower pressure
+1 NM for spare

For example: FL90 to 2000' at 1023 hPa
That's 7 flight levels, so 35 NM, plus 3 miles to slow down, plus 1 mile for the pressure correction, plus 1 mile to spare, total is ~40 miles.
We're not pressurized so max descent is limited to 1000fpm: halving those 40NM to 20NM gives you the limit for a (semi-decent) slam dunk descent and landing, but it's not really a fair comparison in a light twin vs a big jet. With a gear down and full flaps this thing can descend over 4000fpm while still slowing down.

"With a gear down and full flaps" - well, the arrival is flown clean. And jets glide pretty well; typical L/D is around 18:1 which translates to 3NM per 1000ft.

I don't generally plan for long straight-in approaches & descents as I rarely have occasion to do them, but barring any other restrictions the rule of thumb I use for VFR operations in an unpressurized light GA aircraft is "Begin a cruise descent, at no more than 500 feet per minute, such that I arrive at the airport traffic pattern entry at pattern altitude."
You could easily adjust that for a long straight-in to say "…such that I intercept the glide path to the runway somewhere between 3 and 5 miles out without requiring major changes to the aircraft configuration (particularly power/pitch).", or for an instrument approach to say "…such that I arrive at the appropriate fix at the desired altitude, per the approach plate".
I imagine a similar rule of thumb could be established for pressurized/jet aircraft, possibly with a faster descent rate (since you don't have to worry about ear block on the way down).
This indirectly accounts for how much potential energy (altitude) you have to dissipate - you're considering your (ground)speed, starting/ending altitude, and the descent rate you want to maintain (which gives you the distance at which you want to start descending).
The actual descent profile (and your speed profile during the descent) will of course also be modified by the speed and configuration you want when you reach the bottom of the descent - it probably isn't ideal to arrive on a 3 mile final doing 200kts over the ground unless a drag chute is part of your braking routine. (The deceleration requirement is accounted for in the ATC planning formula DeltaLima describes which is also a good starting point for figuring out your descent - for light GA folks like me though you can probably work the speed profile in your head.)

I can't really offer you much for the second half of your question ("How close can you get?") -- That really depends on how high you are starting out (what's your cruise altitude?), the performance characteristics of the airplane (how quickly can you drop altitude?), and how aggressive you want to be as the pilot.
I could conceivably get pretty close in my Cherokee at 5000ish feet AGL flying "straight in", pull the throttle to idle, slip like my life depended on it, and make the runway without carrying too much excess velocity, but it would be particularly ugly to do so, and quite a bit of work for me at the controls.
I would certainly put that in the category of "abnormal operations" (though I also  put that kind of stuff in the "fun to try at a quiet airport with my CFI riding shotgun" category).

Say you're cruising at 17000ft(I know this is low) at a speed of 310 knots and landing at a runway 700ft above sea level. This means you need to descend 16300ft.
First off, cross out the last two figures so you're left with the number 163. You then divide that number by 3 to get 54.3. Let's say you're landing at 200 knots so you need to lose 110 knots.
Divide the speed you've got to lose, so 110, by 10 so in this case you're left with 11. Add that to the first answer, 54.3, and then you have the distance out you need to start your descent at, in this case 65.3 nautical miles.
If there is a tailwind then for each 10 knots minus 1 nautical mile and for a headwind add 1 nautical mile for each 10 knots.
For working out what rate you should descend at, divide your total nautical miles figure, in this case 65.3 by 200. You should get what is rounded to 0.33. Then work out what that is as a percentage of 60. 33% of 60 = 19.8. That's how long the descent will take so divide the altitude you need to lose, 16300ft by the time it will take, so 19.8 minutes but say 20, you just round it. 16300/20 = 815.
This means you will start your descent at 65.3 nautical miles out and descend at a rate of 815 feet per minute. As the fpm goes up in hundreds round down to the nearest 100 so in this case 815 becomes 800.

welcome to aviation.se please consider formatting your answer so that it can be properly read.

Dividing by 200 then multiplying by 60 is a horribly inefficient method and liable to significant errors when done mentally. "Triple and divide by ten" performs the same task, is simpler and already has been done by the time that step is reached.


text:
When might a pilot hand-fly a jet at cruise altitudes, and is it difficult?
How difficult is it to hand-fly a jet at cruise altitudes? Other than autopilot failure and just doing it for the fun of it, when might you want to hand-fly at those altitudes?
I suspect the answer to the first question varies with different aircraft. I have an answer for the 747-100 and -200 series below.

The Lockheed U2 was extremely difficult to hand fly due to it's narrow coffin corner.

@shortstheory IS! We still use the U2!

I was a flight attendant for a major carrier and taking flying lessons back in the early 80's.  When I had about 5 hrs total time, a captain who was a friend of mine allowed me to try and hand fly a 727 at altitude from the right seat while we were over international waters. (Not that that would have mitigated the consequences if it got out what we were doing)  I couldn't do it.  The lag time between input and reaction was just too long for me to get any kind of feel for the controls. I tried for a couple minutes with him continually re-engaging the autopilot after the excursions got too big.

@PJNoes I hope he is not still an active pilot, that is absurd behaviour

@Cloud Whether that is absurd behavior is, of course, a matter of opinion. I can assure you, though, that letting flight attendants handle the controls was often done back in the 1980s and 1990s. Indeed, at the request of the captain, I vacated the f.o. seat of a 727 freighter in the late 1980s so that a jump-seating f.a. could take the controls on an approach into Barcelona, Spain in the middle of the night. The f.a. did a remarkably good job of landing the airplane, closely monitored, of course, and directed by the captain.

@Terry I presume this f.a was an aspiring pilot at least? Did you ever voice your concerns as an F.O of this practise? (p.s if you have any journal entries that detail such an event, please let me know, although I have sifted through a great deal of your website already)

@Cloud As I remember he was an Iberia f.a. working on his private license. The captain asked me if I had any objection. I did not. There's nothing about this in my journal entries because I didn't start the journal until I went to work for Tower Air, and this was back when I was flying for Evergreen International. However, I've started a topic on flying night freight in Spain, https://terryliittschwager.com/talking-of-flying.php#nightfreightspain that will include that and other things I haven't thought of in a long time.

@Terry I am very excited to read some of that! I am already in disbelief at some of the titles... "Valencia to Madrid speed competition", "drunk loaders"... oh dear...:)

For 747-100 and -200 aircraft at 35,000 ft and above, you can do it, but it's hard to keep the airplane within 100 feet of the assigned altitude, and you typically can't do that (or at least I couldn't) without practice. 200 foot altitude excursions were the norm when I first took control if I had not done it for a while. For the few first officers that accepted an invitation to try it, an initial 300 foot altitude excursion was typical when they first tried it, especially immediately after disengaging the autopilot.
I found the concentration required was very tiring. Ten minutes was typically enough to satisfy the urge.
Insofar as when you might want to do it, I found hand-flying produced a smoother ride in heavy to severe turbulence than the autopilot's turbulence mode, which tended to try to keep the assigned altitude and aircraft pitch too slavishly.

Are you even allowed to do it now there is RVSM?

@JanHudec No, handflying is off limits in RVSM airspace.

It helps a lot if you have a good flight director with altitude capture and hold.  Then it isn't quite as big of a deal, though it is still tiring because of the constant concentration that it requires. In the past when an autopilot has failed, I would take turns with the other pilot and we would only fly for 15 minutes at a time.

@janhudec See: Is it legal to fly in RVSM airspace with an inoperative autopilot?

@Lnafziger Using a flight director is cheating! lol
Although I suppose one could say that using the artificial horizon is cheating and one should do it simply by outside visual reference. I tried that once and it simply didn't work for me.

@Terry Haha, he just said hand-fly so a flight director is allowed!  :-)  And yeah, maintaining altitude by outside visual references is basically impossible at that altitude and speed.  If you are 1/2 a degree of pitch off, you will be way off your altitude before you even know it...

@DeltaLima  At the risk of being pedantic, hand-flying IS allowed in RVSM airspace, just not while level.  The rules allow you to climb or descent without the autopilot since "precise altitude control" isn't happening, or even being attempted, when you're following a climb or descent clearance.  For level flight, though, the autopilot is required to be engaged in RVSM airspace (with exceptions as noted in Lnafziger's linked answer).

"an initial 300 foot altitude excursion was typical when they first tried it, especially immediately after disengaging the autopilot" - Wouldn't an altitude excursion immediately upon disengaging the autopilot be more a symptom of a slightly-out-of-trim airplane?

@Vikki We would start the exercise with the aircraft in-trim. The 747-100/200 series had a small window that showed how much elevator the autopilot was holding against the trim, and you could hand-roll the big trim wheel to align the pointers. As I remember if I was in practice the altitude excursion when disengaging the autopilot was negligible. You're right, though, that if you didn't start with the airplane trimmed, the nose-down would be immediate and could be substantial. I used this fact in a Toastmasters humorous speech at https://terryliittschwager.com/hajj4contest.php.

It's probably not a good idea to hand fly jets at cruise altitudes in many cases (US, EU, and others). The reason is that from FL290 to FL410 (29,000 to 41,000 feet standard pressure altitude), a lot of airspace is under RVSM rules (Reduced vertical separation minima).
This means that aircraft are only separated by 1000 feet vertically. One of the requirements for flying in RVSM airspace is a system for automatically maintaining altitude. If this system is not working, either the aircraft must fly at an altitude outside RVSM space (most likely below) or ATC must agree to provide 2000 foot separation above and below from other traffic.
Some examples of this in practice:

Allowed to continue with increased separation
Not allowed to continue, had to return to airport
Did not inform ATC in violation of rules

See the related question for more details:
Is it legal to fly in RVSM airspace with an inoperative autopilot?

You can legally do it at FL430 or above though!

So you can handfly the supersonic Concorde at cruise? YEAHH!

Aerodynamic damping is proportional to density, so all maneuvers require less control input at altitude than near the ground. On the downside, excursions from the trimmed condition produce greater amplitudes before stability pulls the aircraft back. This explains why hand-flying needs more attention at high altitude.

Background: Damping is the reaction of a system to movement, and positive damping means the reaction slows the movement down. Case in point: The horizontal tail. When the pitch attitude changes (say, by a vertical gust which changes lift first on the wing, then on the horizontal tail), the rotation of the aircraft around the Y axis (the one pointing sideways) creates an additional vertical speed on the horizontal tail surface. This vertical speed is proportional to pitch speed (obviously) and the distance between c.g. and tail. This speed changes the local angle of attack by the ratio between the vertical speed and flight speed. Now we are at the core of it: A high flight speed will cause a smaller angle of attack change at the tail for the same pitch rate. Since this angle of attack change creates the damping force (by creating lift on the tail which counteracts the pitch movement), a higher flight speed at the same dynamic pressure will lead to less damping. This is a fancy way of saying that flying in lower density air makes the aircraft more responsive to disturbances.

AF 447 was a case of the autopilot dumping control into the laps of the pilots, at cruise altitude and speed, and they managed to put the aircraft into a fatal high speed stall. At cruise, aircraft will often be fairly close to the edge of the envelope, and, as @PeterKämpf mentioned, you've really got to pay attention to what you're doing, so you don't end up on the wrong side of the limits.

No, Phil, that was an ordinary low speed stall. A high speed stall happens when Mach effects limit the lift coefficient to values below what is required to create sufficient lift. And the cruise altitude of airliners is limited by engine power - they are not (yet) flying in the "coffin corner". Yes, the envelope is smaller, but mostly because of limited thrust.

Sorry, I've frequently heard this case described as a "high speed stall", but maybe everyone saying that is wrong. They had what would normally be considered plenty of airspeed, but raised the nose way too high and stalled as a result. Would that still be considered a "low speed" stall even though they were (AIUI) still at more or less cruising speed?

Yes, this is low speed stall because the dynamic pressure was not high enough to allow the aircraft to fly properly. The angle of attack was well into the stall region, large sections of the wing had separated flow and the drag that goes with it. This drag caused the high sink rate which made AF447 sink from cruise altitude to sea level in just three minutes. They arrived there at the same dynamic pressure at which they started the descent, and then the aircraft was flying really slowly, too.


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Can you re-register a de-registered aircraft with the same N-number?
If I'm selling a plane that has been de-registered, can the new owner re-register the aircraft with the same number (or do they have to get a new one)? Does the airworthiness certificate transfer as well? How long does this process typically take?

The FAA has a page that sort-of takes you through this process.  Basically it boils down to this:
If your registration has expired you still have ~90 days to register the aircraft

If a renewal application was first received by the Registry after the expiration date, the renewal process no longer applies. An aircraft owner may apply for registration of an unregistered aircraft under 14 C.F.R. §4731(a), by filing an Aircraft Registration Application, AC Form 8050-1, the $5.00 registration fee, and evidence of ownership (if it is not already on file at the Registry).

So it's a "new registration", but you can keep your N number. (Yes, you have to use an official, FAA-Provided 8050-1 form - you can't download them anymore. You're also going to want to talk to someone at the Aircraft Registration Branch or your local FSDO before you start filling out forms because you don't want your form to show up after the 90 day window or you wind up in the other category...)
After about 90 days your N number is Cancelled & unavailable for 5 years

When an aircraft registration is not renewed, the cancellation of the N-number assigned to that aircraft will take place approximately 90 days after the expiration of an aircraft's registration. Upon cancellation, an N-number will be unavailable for re-assignment or reservation for a period of five years.

At this point you have to talk the aircraft registration branch, but my understanding is you are out of luck -- That N number is void and a new number will be issued when you register the aircraft (at which point you must apply the new N number to the aircraft in accordance with FAR 45, which typically means repainting at least part of the tail).
You must get a new airworthiness certificate bearing the new registration number from your local FSDO.

In both of these cases your airworthiness certificate is invalid* (because without a valid registration you have no authority to operate the aircraft).
In the first case you will not need a replacement airworthiness certificate (because your N number hasn't changed), but if your N number has been cancelled you will  need a new airworthiness certificate issued with the new N number on it.
Total time for all the paperwork to be processed depends on which bucket you fall into -- the aircraft registration branch usually has about a 30-day backlog (check here), plus time for the post office to move the paper from point A to point B, so a lag of a little over 30 days is what you should expect.
If a replacement airworthiness certificate is required that will probably add a few days to the process as well.

What's the point of making the N-number unavailable for 5 years after it last stopped being used?

Check the FAA's FAQ here.
The N-Number in question cannot be used for 5 years after it expires.
The airworthiness certificate does not change, it is just invalid without current registration. They may, however, send a new one upon re-registering if the registration expired, if the N-Number changes, or if you request a new certificate.
The process usually takes about a month.

you can register the aircraft in a different jurisdiction and use the same last part of the registration and change only the first 1 or 2 codes


text:
What can I do if my carb-heat cable breaks in-flight?
If I'm flying in conditions that are conducive to carburetor icing, and my carb-heat cable becomes in-operable, is there anything I can do to prevent engine failure if my carburetor starts icing up? Assuming there are no immediate landing-areas to stop and fix the problem.

FAA Advisory Circular 20-113 has a few suggestions which may be helpful (particularly the one about climbing) - though it's generally focused on using carb heat as a preventive measure. They don't really talk about dealing with a carb heat cable failure (perhaps we should suggest an update :-).

Well, this depends a little on your situation.
In all cases your goal is get on the ground in a controlled manner that leaves the pilot, passengers, and airframe intact - so obviously you'll be heading for the nearest airport (and if you can get in contact with ATC and explain your situation doing so would be a really good idea).

No signs of carb ice (yet).
If you're flying in conditions conducive to carburetor icing but don't yet have signs of icing there are a few things you can do to help prevent it from forming:

Seek a warmer/drier altitude
There's a wonderful diagram I'm sure everyone has seen that gives an idea of the probability of carb ice. If you can find an altitude where the temperature/dew point spread is less conducive to carb ice formation fly there until you can land.
Lean the mixture (as practical) to limit evaporative cooling from the fuel vaporizing.
This can limit the temperature drop in the carburetor, and if it's only a few degrees of difference between ice and no ice it might help.
Avoid low-power operation (<60% power).
A partially closed throttle plate is more likely to pick up ice (there is a greater pressure drop across the throttle plate which means a greater temperature drop).
"Clear" the engine periodically by opening & closing the throttle.
This helps ensure the throttle plate does not freeze in place, and can dislodge any small ice patches before they become a more serious problem.

I think this would qualify as an "urgency" situation (pan-pan), per this answer.
  If you can get in contact with ATC don't hesitate to let them know that.

Signs of carb ice are apparent.
If you do have signs of carb icing you can do all of the things above too, but how effective they are may vary.
As xpda noted adjusting the mixture can help (typically carb ice makes the engine run over-rich).
In extreme cases wide-open throttle and an aggressively leaned mixture may keep the engine producing power (and will reduce the pressure drop across the throttle plate, possibly bringing the carb temperature up enough that the ice will melt off).
In many light singles your alternate air is the carb heat box, but if you have an alternate air source for the engine besides carb heat that may be worth trying as well (especially if it's in the engine compartment or heated cabin).

Carburetor icing with carb heat inoperative is a bona-fide emergency.
  I can't imagine not making a mayday call in this case. Best-case scenario you wind up making an uneventful landing with fire trucks waiting to greet you ; Worst-case scenario you wind up landing somewhere that's not an airport, but at least someone knows where you are.

Completely agree with pan/pan or mayday.  What's to lose?

+1 - Great adivce. I had heard (by rumor, haven't tried) that if you flip the mags off and back on, you may be able to get a back-fire that will clear the engine as well, any comment?

On some planes, the alternate air source is heated by the engine and may be better than no heat at all. Running the engine leaner can help, because carb ice is blocks the air, making the engine run too rich. A higher RPM can help, but moving the throttle may knock loose the ice and kill the engine.


text:
What military aircraft is in this video still?
I found this image of an aircraft on a video by a friend of mine and I would like to have your help identifying this for me:

Usually you can find them parked at military bases.

Also helps to say at least approximately where your friend saw this, particularly since it's a military plane, and different militaries in different parts of the world have different planes.

That looks like the Lockheed Martin F-35.

Image source

I was going to say F-15, but the jet inlets give it away.

It seems that the chinese copy of F35 can be distinguished by exhaust type.. The picture is an F35 i presume

The J-31 is twin-engined, like the F-15 which also has a similar silhouette from below

@ChrisH: Interesting, yeah it's also similar.  But the ends of the F-15 wings aren't parallel to the fuselage, they taper back inward aft of the wing-tip.  That was another difference I noticed besides the twin vs. single engine.  e.g. google found http://clipart-library.com/clipart/6cyorayzi.htm and http://www.milart.com/product/m_misc_986.html . Also, the F-15's trailing edge is perpendicular to the fuselage, vs. F-35 having a reverse sweep to the trailing edge all the way in.

@PeterCordes yes, there are plenty of differences, but (to me) the number of engines is the most obvious - counting a small number vs comparing angles, which depend a bit on viewing angle.  The J-31 shares the F-35's pointy intakes and the F-15's engine layout, so for the initiated or those with images to compare it's easy to tell them apart.

@ChrisH: For sure, number of engines is the most definitive and easiest to be sure of.  And good point about other features being dependent on viewing angle.  I mostly just commented to record the results of looking for other differences (between F-15 and F-35), in case you or anyone else was curious.


text:
What does "Rotating airfoils of engines" mean in the US Code of Federal Aviation Regulations?
In part 1.1 of the US 14 CFR, definitions and abbreviations, a propeller is defined as:

...a device for propelling an aircraft that has blades on an
engine-driven shaft and that, when rotated, produces by its action on
the air, a thrust approximately perpendicular to its plane of
rotation. It includes control components normally supplied by its
manufacturer, but does not include main and auxiliary rotors or
rotating airfoils of engines.

What is a rotating airfoil of an engine if not a propeller? The italicized section excludes rotors of rotorcraft so what does "rotating airfoils of engines" exclude from the definition of a propeller?

Compressor and turbine blades.  Whether from a turbocharger, a supercharger, turbo-compound, or a turbine (jet) engine.


text:
What is the slowest long haul commercial aircraft in service to this day?
I have been looking at planes used in routes for airlines to see which model was the slowest.But I still don’t know which aircraft is the slowest.
Edit: long haul meaning: SFO-HND
Also, only passenger.
(Sorry if the question was confusing. It’s my first time asking a question on here)

What is it you're hoping to gain by knowing this information? There may be a better question to ask that will get you closer to what you really want.

It might be best to speak to a travel agent.  SFO-HND seems to be trans Pacific from San Francisco to Tokyo.  These days most likely jets, unless the Clipper 314 is still around.

@Leo Are you asking about any long haul route, or only about SFO-HND?

I just noticed this in the question title, "in service to this day". "to this day" means, to me, since the inception of commercial flight. That means that a plane like the DC-3 (cruise speed 180kn) is significantly slower than any of the answers proposed so far, even the Clipper 314 suggested by @RobertDiGiovanni. I don't think this is what the OP is after, but since he hasn't come back to clarify, then the DC3 is my suggestion. I'm sure there are earlier commercial aircraft with slower speeds.

... especially since the DC3 is in service to this day. Probably can't make the SFO-HND crossing, though, at least non-stop.

Not just SFO-HND. I meant routes like that.

The clipper was retire a long time ago by the way.

The A330 has a top speed of 489 knots according to the dubiously accurate Wolfram Alpha.  I do not have a complete list of long haul commercial aircraft, but that might be the slowest of the common ones.
The IL-62, which is allegedly still flying commercially, goes 490 knots according to Wikipedia.


text:
Can a Supersonic aerofoil have Max thickness near the middle?
I’m really unsure about this question:
Can a supersonic aerofoil have maximum thickness near the middle? so by middle of the aerofoil I mean 50% along the chord
Also, how would you actually calculate location of max thickness of aerofoil please?
I haven’t yet come across one aerofoil that can?

If I remember correctly, F-104 used biconvex airfoil therefore with max thickness just in the middle of its chord. And the very first iteration of supersonic airfoils had a typical diamond shape, that is also with max thickness at 50% of the chord

Yes, the lowest wave drag for a given thickness can be achieved by placing the maximum thickness in the middle.
Any body moving through a fluid must push this fluid aside. When this movement happens at supersonic speed, the fluid has to decelerate via a shock which raises density and pressure. Therefore, all forward-facing surfaces will experience a rise in pressure that increases with the square of their angle of inclination. On the opposite, at the rear where the body contracts, the fluid needs to accelerate via an expansion fan and both density and pressure drop so the fluid can fill the space vacated by the moving body. Consequently, all rear-facing surfaces experience lower than ambient pressure, again proportional to the square of the inclination angle.
Placing the maximum thickness in the middle will give the lowest total of both pressure and suction drag. When you move the maximum thickness either fore or aft, in both cases the drag increase on the now steeper surface will be greater than the drag reduction on the surface with the now lower inclination.


text:
On a ducted propeller, how does duct length affect thrust?
So if we are looking at an aircraft with a ducted propeller (or a high bypass turbofan engine), does it matter how long the duct is? As an extreme example, would having a duct that extends 100 feet behind the prop give any added thrust (let's ignore drag/weight effects of the 100 foot duct)? Because from my understanding, thrust is applied directly at the propeller, so it shouldn't matter how long the duct is just as long as it prevents tip vortex effects.
So as a follow up, why do most high bypass turbofan engines have their bypass duct extend back to where the engine core ends?

For the second part of your question, see How do turbofan nacelle lengths compare?

Generally, there are losses due to friction drag in any tube carrying a fluid; therefore, the longer the duct, the more energy is lost from the air stream (this loss appears as back pressure against the fan, so the same power is absorbed at the reduced flow rate).
The higher the flow velocity, the greater these losses, but in a high bypass turbofan, there are other considerations.  Extending the bypass duct past the engine core allows the cool, relatively slow bypass air to mix with the hot, high velocity turbine exhaust, with the main effect of reducing exhaust noise.  The loss with a duct 2-3 meters long rather than half a meter is small; the gain in noise reduction can be large, and mixing the bypass exhaust with the turbine exhaust inside the duct may also give enough augmentation effect to offset the duct losses.


text:
What makes a weight-controlled microlight tumble, and can it recover?
As shown in this video, what causes a weight-controlled microlight to tumble, and is it possible to stop it from tumbling once it starts?

Looks like stall.

The tricky thing about this type of aircraft is that wing camber is influenced by the pressure distribution over the wing. This means the pitching moment of the wing is changed by the pitching motion, causing a lock-in. Also, centrifugal acceleration makes it hard for the pilot to shift his weight any more once the motion has started.

what causes a weight-controlled microlight to tumble

There seem to be several mechanisms. One is an excessively sharp nose-down control input after entering or approaching a stall.

and is it possible to stop it from tumbling once it starts?

Not without an external safety device (presumably a throwable parachute or something similar)

The tumble mode is a little known mode of departure from controlled flight experienced by weightshift controlled microlight aeroplanes. It has been a very significant factor in fatal accident records, being non-recoverable without the use of external safety devices. The mode consists of a nose-down autorotation at a rate of up to 400°/s. The tumble entry mechanism is explained, and advice to operators developed which should prevent tumble entry. Evidence is shown of the nature of the developed tumble – both modelled and through wind tunnel results, which explain how the autorotation occurs. It is also shown how this theory may be applied during testing of an aircraft to develop a tumble resistant aircraft.

See A theoretical and experimental appraisal of airworthiness evaluation techniques for small light aeroplanes

This seems to be an excellent paper 255-page dissertation which contains far far far more than the average reader of this website could ever want to know about this phenomenon.
You should note that this contains stills from the Youtube video in the question. It is therefore directly relevant. If you can find a better analysis I will print out my answer and eat it.

With a 255 pages count, I find it difficult do describe it as a "paper" but rather a book. EDIT: and in fact is a Doctoral dissertation.

@Federico: Good point, amended.

Stall itself causes down pitch moment and weight-controlled aircraft have limited control authority.


text:
What are these three indentations on the SBD's wing?
I was looking at pictures of WWII planes and noticed that the SBD Dauntless had 3 indentations towards the tip of the wing. What were these for?

According to "The Dauntless Dive Bomber of World War Two" by Barrett Tillman, they are "letter-box" anti-stall leading edge wing slots added to improve the planes stability when approaching the 78knot stall speed during landings (and take offs, actually.)
The initial versions tended to not be able to build up enough speed during the (catapult-less) take offs from the carriers of WW2, and would simply drop off the front edge of a carrier. Adding the three slots basically fixed (or lowered) the speed of stall.

Umm, you were right the first time.  Improving the stall speed means lowering it...

But why would that work? Does it increase surface area thus increasing lift?

@JonasG.Drange :) That sounds like an EXCELLENT question to ask...

This is a better picture showing those indentations (or are they?):

Image Source
They appear to be wing slots (or leading edge slots). More details are here and here.

Well spotted!  The text mentions them on this page: http://www.aviation-history.com/douglas/sbd.html .  Prety sure you're right.


text:
What is "Hotel Mode" on a turboprop engine?
I have heard that some aircraft that do not have an APU can run an engine in "Hotel Mode".
What is hotel mode? Are there any advantages to having it instead of an APU?

Well it saves a lot of weight and space that the APU would need. Given the fact that most of the airports in Europe are equipped with GPU, the Hotel Mode is hardly used. Most oftne just minutes before departure

Hotel mode is a feature on ATR 42/72 turboprops replacing an APU by locking the right-hand #2 engine (PW100) with a 'propeller brake' while allowing the turbine, and therefore also the generator, to run, providing electrical power and bleed air.
ATR describes this as the following:

The propeller brake is fitted on a countershaft on the RH engine reduction gearbox in order to stop the propeller (and the power turbine)

HP (High Pressure) spool drives the DC generator.

Bleed pressure is available downstream the HP compressor and supplies both packs.

This picture should give you sort-of an idea of how it works:

If I gather correctly, the propeller drive shaft is locked, and the (HP) compressor shaft is free to run.
Here's another pic of a PW100 engine:

Hotel Mode seems to be generally disliked for a number of reasons:

It's very loud, especially if you're lifting baggage next to it
It consumes a lot of fuel, since you're running a full engine.
It could be dangerous if the propeller brake is in poor condition and suddenly loses its grip.

This configuration is rare, if not unique. The rival Dash-8 has a separate APU, as does the Saab 2000. It was an optional feature on the Fokker 50. The smaller Jetstream 41 only has a battery.
Source: SmartCockpit ATR-72 documents.

Older S-76 helicopters also had hotel mode.  (Not sure if that's what they called it, but they were able to run a main engine with no main rotor rotation).

Does this cause a pressure build-up between the turbines or make it harder to start?

And why is it called "hotel mode" ?

@summerrain hotel mode would be powering all non-propulsion electrical loads on an airplane. It comes from the maritime term, hotel load which is the electrical load for all non-propulsion systems on a ship. - https://en.wikipedia.org/wiki/Glossary_of_nautical_terms#H

The term, hotel mode would be powering all non-propulsion electrical loads on an airplane using the power generating capabilities of the airplane, such as an engine or an Auxiliary Power Unit (APU).
The term comes from the maritime industry from the expression, hotel load. This is the electrical load for all non-propulsion systems on a ship.

https://en.wikipedia.org/wiki/Glossary_of_nautical_terms#H


text:
Why open up the window shades before takeoff and landing?
On commercial airlines, I've noticed that the flight attendants always ask everyone to open up their window shades before landing or takeoff.
I've always wondered why this is. Is it something to do with the mechanics of the plane? Is it some kind of passenger-comfort thing?
I can't imagine what difference this act makes, but the attendants seemed really insistent on it. :)

See also http://aviation.stackexchange.com/questions/170/what-things-can-a-passenger-look-out-for-to-indicate-an-emergency

Back in the late '70s I often flew Allegheny Airlines into Boston's Logan Airport. I generally kept the window shades open so that after landing I could reassure myself that the aircraft had come to rest right-side-up before unbuckling my seat belt.

I've been on as many flights where they are ordered open as on flights where they're ordered closed. All depends on the airline.

@jwenting That's interesting. I've never been on a flight where the shades were ordered closed during takeoff or landing. I've been on several where they were ordered closed while parked at the gate (because it was hot on the ramp) and during cruise (long-hauls, so people can sleep,) but I don't think I've ever been asked to close them during takeoff or landing.

I fly Southwest and I've never heard the FAs tell us to do anything with the windowshades, either open or closed.

@Sean Southwest FTW!

I'm not sure about other countries, but in the USA there is no FAA requirement mandating that the window shades be open for takeoff and landing.
Individual airlines vary in their procedures, with some requiring them to be open while others do not.  This is set by company policy, presumably set by management because they decided that there was/was not a safety benefit in doing so.
As a pilot, I would prefer the window shades to be open all of the time so that even passengers have the chance to point out something that they think might be a problem.  For example, recently a passenger on an airliner noticed a fuel leak and told a flight attendant about it before the airplane took off.
One important thing to keep in mind is that in the event of an emergency evacuation, you should always look out the window before opening an emergency exit to make sure that there isn't a fire or other hazard just outside the door.  This is why a lot of emergency exits don't even have window shades on their windows.
This answer on Skeptics.SE also points out that emergency crews responding to a crash can see through the open windows to better respond and help the people on the airplane.  It also mentions that the passengers eyes will also be more acclimated to the lighting outside the airplane if the window shades are open.  This is also why some airlines have policies requiring the cabin lighting to match the outside light (i.e. the lights will be on bright during the day and dim/out at night).
This answer on Travel.SE also goes into more detail from a person who works in the airline safety industry.

According to the linked article, the fuel leak was noticed by a pilot of another plane, not a passenger.

@egor A person who is a pilot can still be a passenger on an airplane. :-)

I asked the question over @skeptics.se. Nice to see the response from the perspective of an Aviation guy. Created an account just to vote this up.

Interesting to see you (as a pilot) validate the concept that the passengers may be able to see something that the pilot cannot see from the cockpit. I got shot down on skeptics for including that in my answer.


text:
How can I get an FAA Class 3 medical re-examination?
I have some headache problems and my examiner submitted my data for deferred examination on the FAA website.
The results have yet to come back but let's suppose that I fail on this one - can I apply for an examination again after a certain period of time - For instance, when my conditions are better?

There are two processes you can go through if your medical is denied - one is to appeal the denial to the FAA (which you'd do if your AME messed up and you can prove they're wrong), the other is to reapply (which is probably what you'll want to do if you get denied).
When you reapply you're basically starting the medical certification process over from the beginning. You can reapply right away if you want, but practically you would reapply when you've corrected whatever condition(s) caused you to be denied, and go back to your AME with documentation showing that your condition has been corrected (or determined to be benign).
I assume based on your question that you've had to check the "Frequent or Severe Headaches" box, so you will continue to check that box, and may require a Special Issuance medical because of that -- your AME can give you more details if you wind up in this situation.

If you do get denied talk to your AME (and any other doctors you may be seeing) about your next steps before doing anything - obviously medical issues are serious not just because they keep you out of the sky but because your health is important.
You may also want to take advantage of AOPA's Pilot Protection Services - they have folks on staff who are experts at navigating the FAA medical process and can help you out. It could be worth it if you anticipate you'll need assistance with medical certification over the long haul.


text:
Are the window wipers on jet aircraft ever deployed in flight?
Many commercial airliners have car-like window-wipers. I would presume this is for taxiing only, as the wind would surely keep the windows free from water when airborne,  or do they turn them on in flight?
Also, don't these wipers cause a lot of drag, and wouldn't it be more economical to have some kind of air-jet blowing from nozzles to keep the windshield clear?

In the Falcon 50 and 900, we have windshield wipers that we are allowed to use in flight (up to 205 KIAS), but I have never used or seen them used in the eight years that I have been flying them because they simply aren't needed.  They are usually stowed out of the wind stream so don't really cause much drag.
The Learjet's on the other hand DO have hot air that blows on the windshield and we sometimes used it to blow water droplets off of the windshield when on the ground.  However, the primary purpose of the hot air was to heat and defog the windshield.
On a larger airplane, the additional piping, valves, etc. required to get the hot air all of the way up to the windshield actually weighs and costs more than just putting the windshield wipers up there along with electrically heated windshields to keep them from fogging up.

In the EMB-145 we could use the wipers below 170 KIAS. Wipers are really only useful on or near the ground, so this was not a limitation that really mattered.  Our windscreen wasn't the best at deflecting rain, so in heavy precip we would use them inside the FAF when looking for lights/the runway and during taxi to the gate.  On departure we would use them in heavy precip to taxi and takeoff, turning them off in the after takeoff flow.
Other airplanes, as Lnafziger points out have better flow characteristics over the windscreen or blown air and are not equipped with wipers.
In any airplane, the wipers are only potentially useful for ground ops, takeoffs and landings and serve no purpose at altitude.
In addition to the wipers, we were also equipped with an electric defroster to keep the windscreen free of fog and ice, and this was used during the descent from cruise to landing.

On the 747-100 and -200 airplanes we had windshield wipers which we occasionally used on short final in heavy rain. The switches were on the overhead panel on the captain's side, but the usual procedure was to ask the flight engineer to turn them on but to stand by to turn them off if the visibility was worse with them on than off, which was sometimes the case. I only remember leaving them on for the touchdown a couple of times.
We never used them while taxiing that I recall.
They were very noisy, distractingly so.


text:
If the radio fails, can a pilot contact the tower by cell phone?
Is it an accepted practice to notify the tower of a radio failure by cell phone, and use the cell phone as a radio, or are there other ways of dealing with radio failure?

I suspect this depends on the specifics of the situation, but you could certainly try to contact them by phone, but be prepared that they might not answer. If your intention is, for example, to land at a class D airport and you've not yet entered the airspace, you could fly over it until you get their attention (they'll shoot you with a light gun)... then land when they clear you via light signals.

@mah Might want to spin your light signals comment into a full answer, I think that's what he's looking for.

As I pointed out in another answer of mine, it is not legal to use a cell phone in flight, and as another answer to the same question says, it really doesn't work very well anyway..
Now, if the pilot has an emergency, they can exercise the emergency authority of the PIC as allowed in 14 CFR 91.3(b) to go ahead and use the cell phone.  If it is just the radio failure though, that isn't usually an emergency since there are other procedures in place for radio failures.
Radio Failure Procedures
AIM 6-4-1 contains the procedures to use in the event of a radio failure.
Basically, if the pilot is in visual conditions (VMC) and can remain that way, they should fly VFR (visually) and land as soon as practical.  If they can't remain in VMC then there are a number of rules which spell out the route and altitude that they should fly, as well as when they should start an instrument approach.
Once they get to an airport they will still need to get clearance to land if it is a towered airport.
AIM 4-3-13 covers that, and basically the tower will communicate with the pilot via light gun signals:

wow, didn't realize that light signals would trump cell phone...

@flyingfisch Yeah, there usually isn't really much communication needed once you are close to an airport.  They need to clear you to land and clear you to taxi to the ramp and that's about it.  Pretty simple and no need for a phone call.

...and with the noise in a light GA cockpit that light gun is going to be WAY easier to understand than a voice on the other end of a cell phone anyway, unless you have an audio panel in your plane that connects to your cell phone via bluetooth or a cable. If I take my headset off with the engine running in a Piper or Cessna there's no way I'm going to be able to carry on a phone conversation with someone :-)

Technical nit: Actually, the pilot's authority under 14 CFR § 91.3(b) would not authorize the use of the cell phone, since it only allows deviation from 14 CFR § 91 and the cell phone restriction is 47 CFR § 22.925. The pilot-in-command (or person authorized by the PIC) does appear have the authority to use the phone in if in distress (that deliberately has the same meaning in radio-communications and aviation) under 47 CFR § 80.311, which although sub-sectioned under Maritime Service has apparently been carefully worded to apply to aircraft and other vehicles too.

Based on the link I found for 47 CFR - “The use of cellular telephones while this aircraft is airborne is prohibited by FCC rules, and the violation of this rule could result in suspension of service and/or a fine. The use of cellular telephones while this aircraft is on the ground is subject to FAA regulations.”  The FCC also recognizes emergency situations and allows for otherwise out of band emissions in those cases.


text:
When is a VOR shown on maps?
I do not understand when the Compass around a VOR is and is not present on maps.
For example, around Kansas City:

VOR OJC has been deactivated for quite some time now.  But its compass is still present on the latest map revision. (the frequency has hash-marks through it, indicating the deactivated status.

Why hasn't the map been updated to remove the compass?

VOR RIS is still active, but does not have a compass around it.

Why isn't the compass on this active VOR?
Are there any general guidelines for when a compass is present on the map?

See the Interagency Air Cartographic Committee (IACC) Specifications:

[IACC 2] 3.9.3.8 Compass Roses
Compass roses, as illustrated in Appendix 6, shall be shown centered on all VHF NAVAIDs, when space allows.
Preference shall be given to those serving enroute functions or located in areas not served by other VHF NAVAIDs.
[IACC 5] 3.7.4.5 Compasses Roses
Compass roses shall be charted centered on those NAVAIDs which have routes predicated on them. Compass roses may be shown around other NAVAIDs where placement of the compass rose does not create additional unnecessary clutter or congestion. If compass roses overlap and congestion hinders readability, the compass rose of the NAVAID with the most congestion may be deleted. Compass roses shall be shown oriented to slave magnetic North. Cardinal direction values shall not be shown. Compass roses shall be .75" in diameter and in very congested areas may be reduced in size to .5" in diameter.

In groundschool I was taught that this is actually based on VOR service volumes (which otherwise aren't explicitly marked at all on VFR sectional charts): the compass rose is not shown around VORs with Terminal service volumes. This might be a general rule, but it is not entirely true however. You provide a perfect example: OJC and RIS are both Terminal VORs.
The key differences: 1) OJC has the V10-12 airway, and 2) map is more congested around RIS.

In the case of OJC you can see that the frequency has hatching through it denoting that it has been shut down. However you also see a 77 that is not hatched out. This denotes the units TACAN channel (making it a VOR-TAC facility). Although TACAN is mainly a military technology some civilian aircraft are equipped with it. As such the VOR facility may have been shutdown but the TACAN equipment is still up and running thus the compass around it remains.
For VOR RIS  the compass may not be present due to clutter. In some cases things are omitted from VFR maps to reduce clutter. You can find some discussion in this thread here. It seems that in some cases its up to the discretion of the cartographer.

Might be useful to note that a VOR with a TACAN is called a VORTAC, not just a VOR. The FAA is not aggressively maintaining VOR stations anymore (kind of like NDB's), and plans to discontinue about half of the VOR stations by 2020 in favor of WAAS systems and NexGen..

To be strictly accurate, OJC is a VOR-DME, not a VORTAC.

Why hasn't the map been updated to remove the [OJC] compass?
According to the FAA's chart users guide:

NAVAIDS in a shutdown status have the frequency and channel  number
  crosshatched. Use of the NAVAID status “shutdown” is  only used when a
  facility has been decommissioned but cannot  be published as such
  because of pending airspace actions.

Of course, that just changes the question to "what are pending airspace actions"? But the A/FD entry for OJC says it isn't a VOR but rather a VOR/DME:

(T) VORW/DME 113.0   OJC   Chan 77   at Johnson Co Executive. 1034/6E. VOR dcmsnd: DME still operational

So the DME portion of the VOR/DME is still active, even if the VOR itself has been decommissioned (and as @Dave pointed out in his answer, you can also see on the chart itself that the DME channel isn't crossed out). I had a quick look at some of the instrument procedures around there and couldn't immediately see where the DME is used, but presumably someone needs it for something, at least for now.
Why isn't the compass on this active VOR?
Most likely because the map is simply very cluttered at that point; the TEB VOR/DME is another example where there's no rose on the VFR chart (although there is one on the TAC). The LGA and JFK roses already overlap there and adding TEB as well would be quite messy.
I found some discussions online that said a) only terminal VORs may not have a rose; and b) including the rose or not is the chart designer's decision. But there were no sources quoted for either statement.

I can verify that the OJC VOR is not only shut down but disassembled and removed and the DME is still there. Drove by there a while back and the VOR was in pieces and it appears that they moved the DME a couple hundred yards to the east (unless that's where it was to begin with, I'd never noticed it before).


text:
What are the differences between Normal and Utiltiy Categories
In the operating handbooks for GA aircraft, there are often weight and balance limitations listed for both Normal and Utiltity category operation.  If I restrict the loading to the Utility category envelope, I want to know what regulations and prudence allow me to do over the Normal category envelope.
I am guessing that there are a set of regulatory certification standards for each category, as well as a list of specific restrictions for each type certificate.  What are these definitions and where are they found?

has the FAA removed the section in Part 23 on the utility category? I have tried searching in the most recent FARs on CFR.gov, and have not been able to find any definition of utility category or what it is capable of.

From a regulatory standpoint the governing regulation is FAR 23 (airworthiness standards for what we'd generally call "small" airplanes - Normal, Utility, Acrobatic, and Commuter category).
FAR 23.3 is probably what you're interested in, and tells us:

Normal Category is limited to airplanes that have a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for nonacrobatic operation.
They go on to specify that nonacrobatic operation includes:

Any maneuver incident to normal flying
(for very vanilla definitions of "normal" - they expect you to use some common sense here!)
Stalls (except "whip stalls")
What most pilots recognize as the "commercial flight test maneuvers": Lazy eights, chandelles, and steep turns, but with an angle of bank not greater than 60 degrees in any of these maneuvers.

Utility Category is the same type and size of airplane, but approved for "limited acrobatic operations" - this may include intentional spins, as well as the "commercial maneuvers" with higher bank angles (greater than 60 degrees, up to 90 degrees).
Acrobatic Category is the same type and size of airplane, but approved for acrobatics  without any restrictions "other than those shown to be necessary as a result of required flight tests" -- basically "airplanes that can go upside-down".

The commuter category is boring: It's basically the normal category, but with more engines (at least 2) and more seats (up to a maximum of 19). Commuter category aircraft can also have a higher maximum takeoff weight (up to 19,000 pounds).
An aircraft can be certificated in any combination of the Normal, Utility, and Acrobatic categories if the aircraft meets the requirements of the appropriate category (as specified later in FAR 23).  An aircraft certificated in the Commuter category may not be certificated in any of the other categories however.

Generally the restrictions you find on aircraft are not regulatory ones (from the FARs) but Operating Limitations (in the POH or placarded on the aircraft) which you must comply with (per Part 91 of the FARs).
For example, the Cessna 172 and the Piper Warrior are both dual-category aircraft (Normal and Utility), and specify a "Utility Category CG Envelope" in their weight and balance charts.
The Piper Warrior is not approved for spins in the utility category (they are placarded with SPINS PROHIBITED). they also have other restrictions for utility category operations which are found in the POH and on aircraft placards (e.g. UTILITY CATEGORY - NO BAGGAGE OR AFT PASSENGERS, and maximum entry speeds for other acrobatic maneuvers).
Most Cessna 172s are approved for spins in the utility category and are not placarded against them. (Certain aircraft with specific STOL kits installed are disapproved as a result of the kit, and have placards prohibiting them).

has the FAA removed the section in Part 23 on the utility category? I have tried searching in the most recent FARs on CFR.gov, and have not been able to find any definition of utility category or what it is capable of.

I think the info you are looking for was in § 23.2005 Certification of normal category airplanes. It was rewritten sometime after 1996 to remove the utility category but lots of FAA Books and ACs still refer to it. The POH or AFM of many aircraft certified under CAR3 still refer to the utility category when determining the W&B for commercial maneuvers.
This site has an old version. https://www.ascentgroundschool.com/faa-references/fars/107-part-23-airworthiness-standards-normal-utility-acrobatic-and-commuter-category-airplanes#14:1.0.1.3.10.2.59.2


text:
How can I learn about unpublished VFR reporting points?
I often hear "The Creek" used by pilot and ATC in the vicinity of Provo Municipal airport.  I've been flying in this area for over 20 years, and I don't know what they are talking about.  There are at least three rivers that empty into Utah lake in the vicinity of the airport, one of them is named "Hobble Creek", but it would seem presumptuous to assume that is the one that is meant.
I am interested to hear strategies for learning the locations of unpublished, but commonly used waypoints.

http://vfrmap.com/?type=vfrc&lat=40.219&lon=-111.723&zoom=10&api_key=763xxE1MJHyhr48DlAP2qQ  Yup, hard to tell from a sectional what is being referred to.

Find a way to connect with local pilots and ask them

Deer Creek Reservoir maybe?

Deer Creek is up Provo Canyon, with is usually used as a reporting point "Provo Canyon".  Id guess you'd have to be at about 12kf or more to be heard from Deer Creek itself.

Is the term "up the creek" or "without a paddle" ever used?

Wait until the frequency isn't terribly busy on one of your flights, then just:
"Unfamiliar with Creek waypoint, Request clarification"
You can reasonably expect them to either explain the waypoint, or if they're busy, potentially give you a phone number or other contact info to try from the ground.
You can also call an Airport Manager (801-852-6715) for questions.

Its a cloudy day today, low traffic, so I called the tower on the phone.  He seemed surprised when I mentioned that there were three rivers terminating in the lake within his airspace.  We worked out that "the creek" is the Spanish Fork River which terminates on the south shore, roughly inline with an approach to runway 36.

If you don't already have one, get a SLC Terminal Area Chart.  Sometimes they will depict VFR reporting points that the Sectionals will not.
Also, airports themselves will publish local area course rules that contain points like this.  Check with an FBO, flight school, or tower.  And if not published anywhere, just ask as Abelenky suggested.

This is a good Idea.  This does appear to be an unpublished point, however.  It does not appear on the SLC TAC.  A search for "creek" in the SW chart supplement revealed nothing relevant.


text:
What lights does the Cessna 172 light rheostat control?
I am part of a team developing a Cessna 172 P model for FlightGear, an open source free flight simulator. We are now programming how the panel and radio lightning rheostat should work, but we found a lot of unclear and/or contradictory information about it online. Our main problem is to understand how the radio light knob (labelled as RADIO LT) work in these older models of the 172.
The POH from 1982 states the following:

The engine instrument cluster (if post lights are installed), radio equipment, and magnetic compass have integral lightning and operate independently of post or flood lightning. The intensity of this lightning is controlled by the inner knob on the light dimming rheostat labelled RADIO LT; rotate the knob clockwise to obtain the desired light intensity. However, for daylight operation, the compass and engine instrument lights may be turned off while still maintaining maximum light intensity for the digital readouts in the radio equipment. This is accomplished by rotating the RADIO LT knob full counterclockwise. Check that the flood lights/post lights are turned off for daylight operation by rotating the PANEL LT knob full counterclockwise.

This makes it look like the RADIO LT knob controls both the brightness of the radio digital readouts (i.e. the frequency digits) as well as other types of lights (radio cluster buttons and compass), but I found out that other renowned simulations of the 172 for other simulators do not dim the digital readouts with that knob. It also seems strange to me that one would be able to dim the radio digits under any condition, let alone turn them completely off.
So does anyone here have experience with these models of the 172? Would anyone be able to describe how to best model the behaviour of the radio lights?

Well, we are modelling the P variant, but as far as I understand the variants from the late 70's and 80's are all very similar to one another. Also, in case you do have the information concerning other variants, we would be more than happy to hear them because maybe some conclusions could be inferred from it.

Have a look page 355 (of the pdf viewer page number) of this maintenance manual. Here is a snapshot of the related circuit. There are other manuals on the site that may be useful.

The dual knob is clear to us. The outer knob controls the panel lightning, which is some sort of backlight for all gauges. The radio lightning on the other hand is what is confusing us, particularly whether the radio displays with digits should also be dimmed or not

Also thanks for the maintenance manual reference; though I couldn't find a direct answer for this question there, it seems to be a very nice resource

From the drawing, the INST LT rheostat (referenced 6 in an hexagon) should be the PANEL LT mentioned (it could have its name changed over time). INST LT controls both the instrument/panel lighting via the red-white wire, and the compass lighting via the red-black wire and pin 3 of the top connector (which parts are referenced 4 and 5). The RADIO LT which dims the display is completely separate. Here an annotated drawing.

Thanks for the annotated image. But if the INST LT controls the compass light, then it's going against what the POH states above (the compass light should be controlled by the PANEL LT). And as far as I can understand it doesn't contain information about the digital displays in the radio, which is the main thing behind my question.

Let us continue this discussion in chat.

This depends more on the radios installed than the plane its self, older era planes may have had King radios with analog numeric readouts. These radios are generally back lit and controlled by what ever rheostat controls the panel those radios generally look like this

(source)
later planes may have had digital readouts which in some cases had another control to dim the intensity. This is often because in a sense the lights are always on you may need to control them with out turning on or dimming the panel. As a matter of fact you generally want them to work opposite, during the day when the panel is dim or off you want the radio lights to be brightest they would then be dimmed in the evening as you bring the panel lights on. Those radios often looked like this,

(source)
The dim function may appear on units like the DME and Auto Pilot if they are similarly lit.
Its been a while since I have night flown with one but if memory servers the newer GPS units like the GNS430/540 have backlit buttons that come on when the panel lights are activated. These units also tend to have separate ways to control the screen brightness/contrast

(source)
You may have more luck referencing the manuals for the radios them selves than the POH for the plane. You should design for the types of radios you are putting in (looks wise)

The Bendix-King KX-155, KR-87, and KT-76C dim their digits based on built-in photosensitive resistors. The faceplate backlighting and the illumination intensity of the NAV instruments is controlled by the radio dimmer button, which adjusts the voltage they receive via a voltage stabilizer circuit (LM350K). The engine and flight instrument' lighting is controlled by another voltage stablizer adjusted by the instrument dimmer.
Note; the lighting of the magnetic compass is controlled by the pedestal light dimmer!

The light rheostat is generally used to brighten or dim the overhead light used to shed some light on the control panel on older 172's (their all old). It really is useless. Newer ones have a few lights under the edge of the glare shield and the knob controls their intensity. The post light is a light in the post between the glare shield and the cabin roof. It's a white light and not something you want on at night. If you are designing a simulator then make it real. Make the panel almost impossible to see at night. This way the player can get the feel of a real 172. Check out Sporty's pilot shop. That's why they sell lights you can strap to your head. Or lights that clip somewhere so you can see the instruments.